Telephone receiver



April 29, 1941- P, A. BoTToRl-'F 2,239,337

TELEPHONE RECEIVER Filed June 8, 1939 2 Sheets-Sheet l April 29, 1941. P. A. Bo'rToRr-'F TELEPHONE RECEIVER '2 sheets-sheet 2 Filed June 8, 1939 Patented Apr. 29, 1941 TELEPHONE RECEIVER Paul A. Bottori, Des Plaines, Ill., assignor to Electro-Acoustic Engineers, Des Plaines, Ill., a

partnership consriting of Paul A.

Charles A. Betto Bottori and Application June 8, 1939, Serial No. 278,039

Claims.

My invention relates to telephone receivers and particularly 4to receivers for use in conjunction with hearing aid apparatus of the so-called bone conduction type.

In hearing aid apparatus of this type, the sound impulses produced by the receiver are transmitted to the sensory nerves through the bony structure of the head of the user, the sound vibrations being conducted directly to a portion of this bony structure by a vibrating portion of the receiver. Because of this mode of operation, a satisfactory receiver of the bone conduction [type must meet a number of very exacting and to some extent conflicting requirements: First, the device must possess high electrical lto mechanical efficiency; second, in order that the available output of the receiver can be most eilicienitly utilized, the mechanical impedance of the vibrating portion of the receiver should match that of the relatively rigid bony structure which it contacts; third, to provide maximum intelligibility, the response characteristic of the receiver should be high over as wide a band of frequencies as is possible; and, fourth, in contrast with these operational requirements, the

receiver of necessity must be of relatively small physical dimensions and of light weight,

The receivers previously known to the art have not satisfactorily fulfilled the above enumerated requirements. The inertia type receiver, for example, which is one of the best known prior art devices, has a narrow band or peaked response characteristic and an objectionably low natural period of vibration, due apparently to the rather considerable mass of the vibratory portion of the device. Other types have similar deficiencies.

I'he principal object of the present invention, therefore, is to provide an improved receiver of the bone conduction type which shall not only fulfill the above stated requirements more satisfactorily than the devices previously known to the art, but which in addition shall be simple in design and inexpensive to manufacture. This object is attained through the provision of a receiver embodying various novel structural features and arrangements, included among which are a novel form of non-metallic diaphragm for engaging the bone structure of the wearer and a novel, yet simple, electro-magnetic actuating means for such diaphragm.

Other objects and the various advantages and novel features of the receiver of my invention will be made more apparent by reference tothe accompanying drawings and the following description of one preferred embodiment thereof. In the drawings- Figure 1 is a top plan view of a bone conduction receiver embodying the features of the present invention. The cover of the device and a portion of the underlying pole piece structure have been cut away to better illustrate the various structural elements;

Figure 2 is a sectional view on the general line 2-2 of Figure 1;

Figures 3 and 4 are sectional views taken respectively on the lines 3-3 and 4-4 of Figure 2;

Figure 5 is a side elevational view illustrating the complete receiver;

Figure 6 is an exploded perspective view of the receiver; and A Figure 7 is a diagrammatic view illustrating the magnetic circuit of the bone conduction receiver of my invention.

The casing of the receiver illustrated in the drawings is made in two parts, a generally iiat, more or less rectangularly shaped base portion I I and a box shaped cover I3 which is adapted to be releasably attached to the base portion II by any suitable means, such as the screws I5, Both portions of the casing are preferably made of a molded plastic composition such as the phenolic resin condensates sold under the trade name of Bakelite, or the like.

The base portion I I of the receiver, as is shown particularly in Figures 2 and 6,15 provided with an annularly shaped recess Il on its inner side which forms arelatively thin diaphragm I9 located centrally of the base. This diaphragm I9 serves as the vibration conducting member of the receiver, and the outer surface thereof may conveniently be curved inwardly as illustrated in Figures 2 to 5 in order to provide better contact with the bone structure of the user. The edge portions of the base II adjacent the diaphragm I9 are relatively thick and unyielding, and serve as a rigid support both for 'the diaphragm and for Ithe magnet structure of the receiver. The receiver itself is adapted to be held in conventional position on the head of the user by a iiexible band 20 adjustably attached to the cover portion I3 of the receiver, as illustrated in Figure 5, or by a suitable handle.

The magnet structure includes a pair of pole pieces 2| and 23 which are preferably made of soft iron. The pole piece 2| is provided with four lugs 25 having countersunk holes 2'I drilled therein for receiving screws 29 which serve to fasten the electro-magnetic structure to the base portion I5 of the receiver.

A pair/of rectangularly shaped, permanent magnets 3| of suitable high retentivity magnetic material 'cooperate with the pole pieces 2| and 23 to create magnetic fields of the desiredA strength in the two air gaps 33 and 34 formed between the cooperating opposed portions 35 of the pole pieces. The two magnets 3| are permanently held in intimate engagement with the side portion of pole pieces 2| and 23 by means of eight clamping screws 31 which engage suitable threaded openings 38 in two cylindrical spacer members 39 of non-magnetic material and a U-shaped combined spacer and bearing support member 4 also-of non-magnetic material.

During the assembling of the magnet structure, the U-shaped spacer and bearing support mem-- ber 4| and the cylindrical spacer members 39 are first attached to the inner pole piece 2li. Then, the magnets are put in place, and the outer pole piece 23 is fastened to the members 39 and 4|, The members 39 and 4| preferably have a length (the dimension A of/Figure 6) somewhat less than the corresponding dimension (A' of Figure 6) of the permanent-magnets. By virtue of this arrangement, the tightening of the clamping screws 31 draws the cooperating surfaces of the pole pieces 2| and 23 and the permanent magnets 3| into very intimate engagement and assures maximum efiiciency in the magnetic circuit. In addition, the positive mechanical interconnecting of the magnets and pole pieces thereby accomplished provides a permanent magnet structure of great strength and rigidity and is to a considerable extent responsible for the great inherent ruggedness of the receiver of my invention.

An armature which comprises an elongated bar-like member 43 of low retentivity magnetic material, preferably soft iron, is pivotally supported adjacent one of its ends on the U-shaped member 4|, by means of a suitable pivot pin 42, for movement within the spaced air gaps 33 and ings 55 each comprised 550 turns of No. 33 enameled copper wire. Y

The central passageway 58 formed Vin the insulating spools 55 is made sufficiently large to obviate any possibility of interference with the armature 43 during the operation oi the device, and for convenience in positioning and supportlng the windings 55, it is desirable that the end portions `of the spools shall be square with an area substantially equal to the cross sectional area of the space between the magnets and the pole pieces. The windings v55 `are connected in series, and the ends of the interconnected windings are in turn connected to socket type connectors 59 molded into an upstanding portion Slofthebasell.

The magnetic circuit and the mode of operation of the receiver may best be understood by reference to Figure '7, wherein the ring 3| is representative of the two permanent magnets 3|. As will be seen by reference to that gure, the magnetic eld across both of the spaced air gaps 33 and. 34 is in the same direction. l By virtue of this, the reaction forces between the air gap 34. To minimize friction, it is desirable that the pivot support for the armature shall include jeweled bearings 44, and for most satisfactory results, it appears that the axis of movement of the armature 43 should be located as close to one of the air gaps as is possible.

I'he armature 43 is adjustably connected to the diaphragm portion |9 of the base El by `means of a rod-like stylus member 45 which is brazed or otherwise rigidly attached at its inner end to the central portion of the armature. A suitable opening 46 is provided for the stylus in the pole piece 2|. As illustrated particularly in Figure 2, the stylus 45 is provided at its outer end with an enlarged threaded portion 41 which is adapted to be engaged by an adjusting nut 49, the inner surface of which bears against a shoulder 50 formed in a metallic insert 5| which is molded integrally with the diaphragm I9. The stylus 45 is locked in place by a suitable threaded locking and sealing disc 53 which engages threads formed in the diaphragm insert 49.

Vibratory movement of the armature 43 and diaphragm |9 in response to microphone voice currents or other energizing means is accomplished by means of two coil windings 55 located in the rectangular space between the magnets 3| and the pole pieces 2| and 23. Each of the windings 55 preferably comprises a large number of turns of very fine copper wire wound on a suitable insulating spool 51. In one satisfactory embodiment of the invention the windfields and the eld created in the movable armature 43 in response to the ow of voice currents set up in the windings 55 by the microphone 33 and battery 65, or other energizing means, will cause rotation 4of the armature and corresponding movement of the diaphragm i9. Moreover, any rotative movement of the armature. away from its normal central position in the air gaps will tend to increase the reaction force producing such movement by providing a path of pro- 'gressively decreasing reluctance through the right hand portion 35 of one pole piece, through the armature, and thence through the left hand portion 35 of the other pole piece. lThis eect intensifies the response of the armature to its energizing currents and produces a much more sensitive instrument than any of the prior known devices,

The structural features and arrangement of the armature 43, and the associated magnet structure and diaphragm I9, constitute the most important features of the present invention. For best results in the ordinary types of deafness, a bone conduction type hearing aid receiver should have a mechanical lresonant frequency at about 1800 cycles per second, and the receiver should provide substantial uniform response (within 10 or 15 decibels) over the range from 500 to 3500 or 4000 cycles per second.

The prior art bone conduction type receivers, in part due to the relatively great weight of the vibratory portion thereof (10 to 12 grams in practical umts), have a maximum mechanical resonant frequency at about 1000 to 1500 cycles per second, and what is more serious, have a rather sharply peaked response characteristic (resulting in the output being down at least 2,0 decibels at a frequency of 2000 cycles per second, and greater still for higher frequencies). The structural arrangement of the present invention, however, makes possible a receiver wherein the total weight of the vibratory portion thereof is within the range of l to 4 grams, with the result that mechanical resonant frequencies ofthe order of 1800 cycles persecond are readily attainable. Moreover, the relatively light weight vibratory portion of the receiver of the present invention provides a much more uniform and much higher response characteristic over the entire range of 500 to 4000 cycles than has ever been attained heretofore; output substantially lmiform Aas before prescribed can be obtained. Under standard manufacturing practices, it is preferred that the total weight of the vibratory portion of the receiver of my invention shall be within the range of 11/2 to 2 grams.

In addition to the increased frequency of me- 'chanical resonance and the more uniform respense characteristic made possible by the improved armature and magnet structure of the present invention, a further desirable characteristic results from the fact thatl the mechanical resonant frequency of the receiver can be readily changed by merely changing the thickness of the diaphragm portion I9. This is most important in the provision of hearing aid apparatus for deaf persons whose hearing is not uniformly impaired over the total band of audible frequencies. In many such instances, the utilization of a receiver which is mechanically resonant, and hence yields its maximum output in that portion of the frequency band where the hearing is most impaired, will make it possible for the user to distinguish sounds much more clearly than is possible with standard frequency receivers. Heretofore, however, the excessive cost of manufacturing a line of receivers resonant at various non-standard frequencies has almost precluded the use of anything but standard frequency apparatus. 'I'his present invention fully remedies this situation, since a complete line of receivers resonant at various other than standard frequencies can be supplied by the use of one standard mechanism and a series of base portions II having diaphragms of different thickness.

Tests have shown that a hearing aid receiver of the type disclosed herein may be used as a microphone with very satisfactory results, the receiver when so used being held in contact with the throat of the wearer by a suitable band or clamp. While the efficiency is somewhat less than that of the more conventional forms of microphone, the receiver when so used has particular application in places where the surrounding noise level is extremely high, as for example, in an airplane or in the broadcasting of sports events. In these instances the microphone will pick up very little, if any, of the surrounding noise, although by suitable amplification it will clearly transmit the sound vibrations of the voice of the wearer.

In the foregoing I have disclosed the features of an improved bone conduction type receiver. 'I'he receiver of my invention utilizes a. novel vibratory system of a type very different from any previously known to the art, and in addition it utilizes a novel electro-magnetic system for operating this vibratory means. It will be evident to those skilled in the art that various devices may be developed utilizing the principles which I have disclosed in the foregoing. Accordingly, it is my desire that the accompanying claims shall be accorded the broadest possible construction consistent with the language appearing therein and the prior art.

I claim the following as my invention:

1. In a receiver of the class described, a casing which includes a plate member of non-magnetic material having relatively rigid edge portions and a centrally located, relatively flexible diaphragm portion which constitutes the vibratory element of said receiver for contactmga portion of the bony structure of the user of sald receiver, and means located within said casing I material, having a centrally for actuating said vibratory element, said last vmentioned means comprising a stationary permarient magnet structure which is iixedly attached to` the rigid edge portions of said plate member and which includes cooperating pole pieces for creating two separate magnetic fields spaced some distance from each other, an armature comprising an Velongated bar member of magnetic material plvotally supported upon a stationary support means which is flxedly attached to the rigid edge portions of said plate member, said armature having a portion located within each of said spaced magnetic fields, and means mechanically connecting said armature to the diaphragm portion of said plate member.

2. In a receiver for use in conjunction with bone conduction hearing aid apparatus and the like, in combination; a plate member of nonmagnetic, molded material, having an annularly shaped recess for providing a relatively flexible diaphragm portion which constitutes the vibratory element of said receiver, the edge portions of said plate member adjacent said diaphragm portion being relatively rigid; a first pole piece in the form of' a thin plate member, with diametrically disposed inwardly-turned sections, secured fiatwise to said relatively rigid edge portions; a second pole piece in the form of a thin plate member with diametrically disposed inwardly-turned sections; means for mounting said second pole piece in spaced relationship with said first pole piece soas to bring said diametrically disposed inwardly-turned sections of the second pole piece into spaced registration with the corresponding diametrically disposed inwardlyturned sections of said ilrst pole piece to thereby provide a pair of diametrically spaced air gaps therebetween; a pair of permanent magnets secured between opposite sides of said pole pieces;

said pole pieces and permanent magnets included therebetween providing a permanent magnet housing structure with spaced apart magnetic fields in said air gaps between each pair of said registering spaced apart inwardly-turned sections; an armature extending between said spaced apart magnetic fields; armature support means; bearing means for pivotally mounting said armature adjacent to one end thereof in said armature support means; and adjustable means operatively connecting said armature at a point in between said spaced apart magnetic fields to the center of said annular diaphragm portion.

3. In a receiver for use in conjunction with bone conduction hearing aid apparatus and the like, in combination; a generally rectangularly shaped plate member of non-magnetic, molded located annularly shaped recess for providing a relatively flexible diaphragm portion which constitutes the vibratory element of said receiver, the edge portions of said plate member adjacent said diaphragm portion being relatively rigid; a first pole piece in the form of a generally rectangularly shaped thin plate member secured fiatwise to said relatively rigid edge portions and covering said diaphragm portion; pole extensions inwardly-turned from the opposite ends of said first pole piece; a second pole piece in the form of a thin generally rectangularly shaped thin plate member; pole extensions inwardly-turned from the opposit-e ends of said second pole piece; means for mounting said second pole piece in substantially parallel spaced relationship with said first pole piece so as to bring said pole extensions into spaced apart register to provide a pair of air gaps between the ends of said pole pieces; a pair of generally rectangularly shaped permanent magnets clamped between opposite sides of said pole pieces; said pole pieces and permanent magnets clamped therebetween providing a permanent magnet box-shaped housing structure with magnetic elds at the opposite ends thereof between said registering spaced apart pole extensions; a bar-shaped armature extending between said] magnetic elds; a U-shaped support member se-I cured to said first pole piece and disposed in one end of said box-shaped housing Structure; bear-1 ing means for pivotally mounting said armature adjacent one end thereof between the arnis of said U-shaped support member; and adjustable means operatively connecting said armature at a point in between said spaced apart magnetic iields to the center of said annular diaphragm. portion; the distance between said magnetic iields and the length of said armature both beingI at least as great as the outside diameter of said annular diaphragm portion.

4. In a. receiver for use in conjunction with bone conduction hearing aid apparatus and the like, in combination; a plate member of nonmagnetic, molded material, having an annularly shaped recess for providing a relatively flexible diaphragm portion which constitutes the Vibratory element of said receiver, the edge portions of saidplate member adjacent said diaphragm portion being relatively rigid; a first pole piece in the form of a thin'plate member, with diametrically disposed inwardlyturned sections, secured fiatwise to said relatively rigid edge portions; a second pole piece in the form of a thin plate member with diametrically disposed inwardlyturned sections; means for mounting said second pole piece in spaced relationship with said flrst pole piece so as to bring said diametrically disposed inwardly-turned sections of the second pole piece into spaced registration with the corresponding diametrically disposed inwardly-turned sections of said first pole piece to thereby provide a pair of diametrically spaced air gaps therebetween; a pair of permanent magnets secured between opposite sides of said pole pieces; said pole pieces and permanent magnets included therebetween providing a permanent magnet housing structure with spaced apart magnetic elds in said air gaps between each pair of said registering spaced apart inwardly-turned sections; an armature extending between said spaced apart magnetic fields; armature support means secured to said first pole piece;l bearing means for pivotally mounting said armature adjacent to one end thereof in lsaid armature support means; a longitudinally split winding disposed Within'said permanent magnet housing structure and surrounding said armature for energizing the same;

and adjustable means passing through the split section of said winding and mechanically connecting said armatureat a point in between said spaced apart magnetic fields with the center of said diaphragm portion.

5. In a receiver for use in conjunction with bone conduction hearing aid apparatus and the like, in combination; a generally rectangularly shaped plate member of non-magnetic, molded material, having a centrally located, annularly shaped recess for providing a relatively ilexible diaphragm portion which constitutes the vibratory element of said receiver, the edge portions of said plate member adjacent said diaphragm portion being relatively rigid; a rst pole piece in the form of a generally rectangularly shaped thin plate member secured atwise to said rela,- tively rigid edge portions and covering said daphragm portion; pole extensions inwardlyturned from the opposite ends of said rst pole piece; a second pole piece in the form of a generally rectangularly shaped thin plate member; pole extensions inwardly-turned from the opposite ends of said second pole piece; means for mounting said second pole piece in substantially parallel spaced relationship with said first pole piece so as to bring said pole extensions into spaced apart register to provide a pair of air gaps between the ends of said pole pieces; a pair of generally rectangularly shaped permanent magnets clamped between opposite sides of said pole pieces; said pole pieces and permanent magnets clamped therebetween providing a permanent magnet box-shaped housing structure with magnetic fields at the opposite ends thereof between said registering spaced apart pole extensions; a bar-shaped armature extending betweensaid magnetic ields; a U-shaped support member secured to said rst pole piece and disposed in one end of said box-shaped housing structure; jewelled bearing means for pivotally mounting said armature adjacent one end thereof between the arms of said U-shaped support member; a pair of co-axiaily spaced apart windings connected in series' circuit relationship wound on rectangularly shaped spools disposed within said permanent magnet box-shaped structure and surrounding said armature for energizing the same; and adjustable means passing through the space between said windings and mechanically interconnecting said armature at a point in between said spaced apart magnetic fields to the center of said diaphragm portion; the distance between said spaced apart magnetic elds and the length of said armature both being substantially equal to the outside diameter of said annular diaphragm portion.

PAUL A. BO'ITORFF. 

